The present invention relates to a method and apparatus for separating a plate member such as a bonded substrate stack, a semiconductor substrate manufacturing method, and a semiconductor device manufacturing method.
A substrate (SOI substrate) having an SOI (Silicon On Insulator) structure is known as a substrate having a single-crystal Si layer on an insulating layer. A device using this SOI substrate has many advantages that cannot be achieved by ordinary Si substrates. Examples of the advantages are as follows.
(1) The integration degree can be increased because dielectric isolation is easy.
(2) The radiation resistance can be increased.
(3) The operating speed of the device can be increased because the stray capacitance is small.
(4) No well step is necessary.
(5) Latch-up can be prevented.
(6) A complete depletion type field effect transistor can be formed by thin film formation.
Since an SOI structure has the above various advantages, researches have been made on its formation method for several decades.
As a method, an SOI structure is formed by bonding a single-crystal Si substrate to another thermally oxidized single-crystal Si substrate by annealing or an adhesive. In this method, an active layer for forming a device must be uniformly thin. More specifically, a single-crystal Si substrate having a thickness of several hundred micron must be thinned down to the micron order or less.
To thin the substrate, polishing or selective etching can be used.
A single-crystal Si substrate can hardly be uniformly thinned by polishing. Especially, in thinning to the submicron order, the variation range is several ten %. As the wafer size becomes large, this difficulty becomes more pronounced.
The present applicant has disclosed a new SOT technique in Japanese Patent Laid-Open No. 5-21338. In this technique, a first substrate obtained by forming a porous layer on a single-crystal Si substrate and a non-porous single-crystal layer on its surface is bonded to a second substrate via an insulating layer. After this, the bonded substrate stack is separated into two substrates at the porous layer, thereby transferring the non-porous single-crystal layer to the second substrate. This technique is advantageous because the film thickness uniformity of the SOI layer is good, the crystal defect density in the SOI layer can be decreased, the surface planarity of the SOI layer is good, no expensive manufacturing apparatus with special specifications is required, and SOI substrates having about several hundred-xc3x85 to 10-xcexcm thick SOI films can be manufactured by a single manufacturing apparatus.
To separate the bonded substrate stack into two substrates without breaking the first and second substrates, the following methods are available: the two substrates are pulled in opposite directions while applying a force in a direction perpendicular to the bonding interface; a shearing force is applied parallel to the bonding interface (for example, the two substrates are moved in opposite directions in a plane parallel to the bonding interface, or the two substrates are rotated in opposite directions while applying a force in the circumferential direction); pressure is applied in a direction perpendicular to the bonding interface; a wave energy such as an ultrasonic wave is applied to the separation region; a peeling member (e.g., a sharp blade such as a knife) is inserted into the separation region parallel to the bonding interface from the side surface side of the bonded substrate stack; the expansion energy of a substance filling the pores of the porous layer functioning as the separation region is used; the porous layer functioning as the separation region is thermally oxidized from the side surface of the bonded substrate stack to expand the volume of the porous layer and separate the substrates; and the porous layer functioning as the separation region is selectively etched from the side surface of the bonded substrate stack to separate the substrates.
As a bonded substrate stack separating method, the present applicant has disclosed an epoch-making technique in Japanese Patent Laid-Open No. 11-45840 (Japanese Patent No. 2877800). In the separating method described in Japanese Patent Laid-Open No. 11-45840, a fluid is injected to the side surface of a bonded substrate stack having a porous layer, thereby separating the bonded substrate stack into two substrates.
More specifically, in the separating method described in Japanese Patent Laid-Open No. 11-45840, for example, a bonded substrate stack is held by a pair of holders (substrate holding sections) each having a diameter smaller than that of the bonded substrate stack. A fluid is injected to the side surface of the bonded substrate stack while rotating it, thereby separating the bonded substrate stack into two substrates at the porous layer.
The present applicant has also disclosed in Japanese Patent Laid-Open No. 2000-077286 an improved technique of the separating method described in Japanese Patent Laid-Open No. 11-45840. The separating method described in Japanese Patent Laid-Open No. 2000-077286 separates a bonded substrate stack that is sandwiched from the sides and supported by a pair of support sections. In this separating method, a support region where the bonded substrate stack is sandwiched from the sides and supported by the pair of support sections is changed halfway during separation processing. With this change in bonded substrate stack support region, a region other than the region where separation is progressing is supported by the pair of support sections. According to this method, since the progress of separation is not influenced by the pair of support sections, separation progresses at high efficiency and reproducibility.
However, when the substrate is sandwiched from the sides and supported, supported portions may be soiled or damaged.
In addition, as semiconductor devices are micropatterned or highly integrated, a new requirement is arising for substrates such as SOI substrates. Conventionally, only the upper surfaces of substrates such as SOI substrates are regarded as important. The requirement for their lower surface state is relatively lenient. However, along with an increase in micropatterning and integration degrees of semiconductor devices, damages to the lower surfaces of substrates come into question. If the lower surface is damaged, a given planarity of the substrate is not ensured when the substrate is placed on the wafer stage of, e.g., an exposure apparatus and subjected to exposure. Hence, it is difficult to accurately transfer a fine pattern.
The present invention has been made in consideration of the above situation, and has as its object to support a plate member such as a bonded substrate stack without coming into contact with one surface of the member and also to efficiently progress separation.
According to the first aspect of the present invention, there is provided a separating apparatus for separating a plate member having a separation layer at the separation layer while horizontally supporting the plate member, comprising an ejection section which ejects a fluid toward a recess portion on an outer side of the plate member so as to separate the plate member at the separation layer, a first support section which comes into contact with a first region that is a central portion of a lower surface of the plate member to support the plate member without coming into contact with an upper surface of the plate member, a second support section which comes into contact with only a second region of the plate member except the central portion of the lower surface of the plate member and the upper surface of the plate member to support the plate member while regulating a horizontal position of the plate member, and a control section which causes the first support section to support the plate member at a first stage of separation processing of the plate member and causes the second support section to support the plate member at a second stage of the separation processing, wherein the separation processing is executed in a state in which a space is ensured on the upper surface of the plate member.
According to a preferred aspect of the present invention, the second region is, e.g., an edge portion of the plate member. In addition, the state in which the space is ensured on the upper surface of the plate member is, e.g., a state in which the upper surface of the plate member is not in contact with any support member.
According to a preferred aspect of the present invention, this separating apparatus preferably further comprises a rotating mechanism which rotates the plate member in a horizontal plane by rotating the first support section.
According to a preferred aspect of the present invention, the second support section preferably supports the plate member in a stationary state.
According to a preferred aspect of the present invention, preferably, this separating apparatus further comprises a driving mechanism which moves at least one of the first support section and the second support section, and at transition from the first stage to the second stage of the separation processing, the control section causes the driving mechanism to operate, thereby causing the second support section to support the plate member that has been supported by the first support section.
According to a preferred aspect of the present invention, this separating apparatus preferably further comprises a position adjustment mechanism which adjusts a position of the ejection section so that the fluid ejected from the ejection section is injected into the separation layer of the plate member.
According to a preferred aspect of the present invention, the plate member has, e.g., a disk shape.
According to a preferred aspect of the present invention, the separation layer is formed by, e.g., anodizing or ion implantation.
According to the second aspect of the present invention, there is provided a separating method of separating a bonded substrate stack, formed by bonding a seed substrate having a separation layer and a transfer layer on the separation layer to a handle substrate, into two substrates at the separation layer, wherein the first support section of the separating apparatus according to the first aspect of the present invention is caused to support the bonded substrate stack while keeping the handle substrate on an upper side, and the bonded substrate stack is separated into two substrates at the portion of the separation layer by the separating apparatus.
According to the third aspect of the present invention, there is provided a separating method of separating a plate member having a separation layer at the separation layer by injecting a fluid into the separation layer while horizontally supporting the plate member, comprising the first step of, in a state in which a space is ensured on an upper surface of the plate member having a recess portion on an outer side, supporting the plate member while coming into contact with a first region that is a central portion of a lower surface of the plate member and without coming into contact with the upper surface of the plate member, and the second step of, in the state in which the space is ensured on the upper surface of the plate member, supporting the plate member while coming into contact with only a second region of the plate member except the central portion of the lower surface of the plate member and the upper surface of the plate member, and regulating a horizontal position of the plate member.
According to a preferred aspect of the present invention, the second region is, e.g., an edge portion of the plate member. In addition, the state in which the space is ensured on the upper surface of the plate member is, e.g., a state in which the upper surface of the plate member is not in contact with any support member.
According to a preferred aspect of the present invention, in the first step, preferably, a peripheral portion of the plate member is separated at the portion of the separation layer by injecting the fluid into the separation layer of the plate member while rotating the plate member in a horizontal plane.
According to a preferred aspect of the present invention, in the second step, preferably, a central portion of the plate member is separated at the portion of the separation layer while supporting the plate member in a stationary state.
According to a preferred aspect of the present invention, the plate member has, e.g., a disk shape.
According to a preferred aspect of the present invention, the separation layer is formed by, e.g., anodizing or ion implantation.
According to a preferred aspect of the present invention, preferably, the plate member is a bonded substrate stack generated by bonding a seed substrate having a separation layer and a transfer layer on the separation layer to a handle substrate, and in the first and second steps, the bonded substrate stack is supported while keeping the handle substrate on an upper side.
According to the fourth aspect of the present invention, there is provided a semiconductor substrate manufacturing method comprising the steps of generating a bonded substrate stack as a plate member by bonding a seed substrate having a separation layer and a transfer layer on the separation layer to a handle substrate, and in a state in which the bonded substrate stack is horizontally supported while keeping the handle substrate on the upper side, separating the bonded substrate stack into two substrates at a portion of the separation layer by applying the separating method according to the third aspect of the present invention.
According to the fifth aspect of the present invention, there is provided a semiconductor device manufacturing method comprising the steps of preparing an SOI substrate manufactured by applying the manufacturing method according to the fourth aspect of the present invention, and element-isolating an SOI layer of the SOI substrate and forming a transistor on the element-isolated SOI layer.
According to a preferred aspect of the present invention, the transistor is a partially depleted FET or a fully depleted FET.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.